Various devices are known that detect a vascular pattern in a portion of an individual's retina to identify the individual. Examples of such devices are disclosed in U.S. Pat. Nos. 4,109,237; 4,393,366; and 4,620,318. In these devices, a collimated beam of light is focused on a small spot of the retina and the beam is scanned in a circular pattern to generate an analog signal representing the vascular structure of the eye intersecting the circular path of the scanned beam. In the U.S. Pat. No. 4,393,366 , the circular pattern is outside of the optic disk or optic nerve and in the U.S. Pat. No. 4,620,318, the light is scanned in a circle centered on the fovea. These systems use the vascular structure outside of the optic disk because it was thought that only this area of the retina contained sufficient information to distinguish one individual from another. The light is scanned in these systems in order to provide sufficient contrast between the vascular structure of the eye outside of the optic disk and the background pigment of the retina. However, systems that use scanners are typically large, complex, expensive and fairly delicate. Moreover, the tilt of the eye can change the retinal structure “seen” by these systems such that two distinct points on the retina can appear to be superimposed. As such, the signal representing the vascular structure of an individual as generated by these systems will vary depending upon the tilt of the eye. This problem is further exacerbated because these systems provide data representing only that vascular structure which intersects the circular path of scanned light, if the individual's eye is not in exactly the same alignment with the system each time it is used, the scanned light can intersect different vascular structures, resulting in a different signal pattern for the same individual. Problems in consistently generating the same signal pattern for an individual make it difficult to use such systems for identification purposes.
Portable systems used by doctors to view the fundus of a patient's eye and capture an image thereof for diagnostic purposes are also known as shown in U.S. Pat. Nos. 5,861,938; 5,861,939 and 5,673,097. These systems scan light using a laser or multiple, sequentially actuated light emitting diodes. However, the image viewed or captured varies with the positioning of the device by the doctor with respect to the patient's eye.